Figure 2.

CD64 expression is inducible by IFN-I and TLR agonists. (a) Effects of recombinant IFN-α (4 ng/ml) on mRNA and protein expression of monocyte markers. Mean differences (fold increase/decrease versus control) in mRNA expression in PBMCs treated with PBS or IFN-α (n = 4 per group) were determined with real-time PCR. Changes in cell-surface protein levels on monocytes (MFI) were measured with flow cytometry. Positive values denote increased expression after IFN-α treatment compared with controls (PBS). (b through d) Dose-response analysis of CD64 (b), CD16 (c), and CD32 (d) expression in vitro on IFN-α-stimulated monocytes from healthy controls. In some groups, B18R (0.1 μg/ml) was added 1 hour before stimulation with IFN-α. (e) Induction of monocyte CD64 surface expression by R848 (1 μg/ml), CpG-DNA (10 ng/ml), LPS (1 μg/ml), or IFN-α (4 ng/ml) in the presence/absence of B18R (added 1 hour before stimulation). Flow-cytometry analysis was performed 19 hours after stimulation. Values represent the mean ± SEM from three independent experiments. *P < 0.05 (Student's t test).